The tongue is sensitive to five tastes: salt, sweet, bitter, sour, and “umami” in Japanese language, the taste of glutamate. There is no analogous word to describe this taste quality in the English language. “Umami” is used by the Japanese to describe the taste of monosodium glutamate (MSG, the sodium salt of the amino acid glutamic acid) as well as the taste of ripe tomatoes or the meaty taste of certain fish and broth. It should be noted that although glutamate is often referred to as flavour enhancer, this is probably incorrect as the umami taste is a taste on its own.
Monosodium glutamate (also know as Ve-Tsin or E621) is a controversial additive. However, clinical studies have so far given no reasons for concern. Hence, whereas MSG or glutamate can actually aid to providing healthier eating habits, consumer acceptance is generally low, even despite the proven safety of MSG. There is thus a need for umami-active compositions that are label friendly or that do not have to be mentioned on the labels at all.
One such composition has been described in WO 99/60868, which relates to a clear tomato concentrate comprising hydrolyzed tomato proteins. The clear tomato concentrate of WO 99/60868 is produced by processing tomatoes into two fractions, the serum and the pulp, and concentration of the serum to a value of e.g. 80 Brix, followed by hydrolysis (enzymatic or acid) of the concentrated serum. In an alternative embodiment, the serum is first hydrolyzed and then concentrated. The so obtained clear tomato concentrate may subsequently be dried.
WO 2008/040611 describes a method of producing a fractionated tomato extract having a pH of at least 4.6, when having a Brix value of 1.0; comprising 2.5-95 wt % of glutamic acid, based on the dry weight thereof; having a weight ratio of total glutamic acid to citric acid of at least 0.8 and a lycopene level of below 50 ppm, based on the dry weight of the extract, said process comprising the subsequent steps of preparing tomato serum and hydrolysing the proteins contained in the tomatoes from which the serum is prepared; subsequently fractionating the serum into two or more fractions, one fraction being rich in glutamic acid and low in citric acid and lycopene. The tomato fraction contains increased amounts of gamma-aminobutyric acid (GABA). Sugars, in particular the monosaccharides glucose and fructose, are considered to enhance the umami taste, and are kept within specific limits of monosaccharide to glutamic acid ratio.
WO 2009/080763 and WO 2010/079013 describe processes for producing an umami-active tomato fraction, involving the subsequent steps of providing a tomato serum, preferably substantially free from sucrose; separating the serum into two or more portions: at least one first portion and at least one second portion whereby the at least one first portion is lower in lycopene than the at least one second portion; concentrating the at least one first portion low in lycopene; fractionating the lycopene-depleted concentrated serum into fractions with well-defined w/w ratio of citric acid to glutamic acid (C/Glu). The umami-active tomato fractions obtained in '763 and '013 are characterized by comprising relative high levels of glucose and/or fructose and low levels of glutamic acid, and have glucose to glutamic acid ratios in excess of 4.
WO 2010/069743 relates to a liquid umami-enhancing composition for use in food products having very low levels of glutamic acid while maintaining an umami taste perception similar to products with normal levels of glutamic acid. The composition is characterized by a w/w ratio of glutamic acid to citric acid of at most 0.6 and comprises at most 2 wt % of glutamic acid.
The above-described methods suffer from the drawbacks that they produce a rather crude umami fraction and/or that the fractionation process is inefficient.